The aim of the marriage (same-sex couples) bill is to ensure that all couples enjoy equal marriage rights. Some elements of legal asymmetry remain, however, under the legislation.

Those who draft the parliamentary bills have been unable to define what constitutes consummation of a same-sex union. Consequently there is no provision for divorce on the grounds of non-consummation of a gay marriage.

That problem also means that same-sex couples who wish to divorce will not be able to cite adultery with someone of the same sex – the civil servants similarly struggled to find a definition of adultery between two men or two women.

Adultery will, nonetheless, be a permitted grounds for divorce if it follows sexual intercourse between one of the couple and someone of the opposite sex. That, at least, is consistent with existing marriage laws: if a man decides he is gay and leaves his wife for a man, she can divorce him for unreasonable behaviour but not adultery, which is defined as sexual intercourse.

Divorce lawyers do not expect the new law to have a significant impact on settlements when relationships break down. "An appeal court hearing last year, in the case of Lawrence and Gallagher, established that separations by same-sex couples in civil partnerships are like other divorces," said William Healing, a partner at the law firm Kingsley Napley, who specialises in family cases.